6of8Visitors make sand castles on the beach at South Padre Island.Photo: Pam LeBlanc, staff writer

7of8Pink flowers grow on the dunes on a South Padre Island beach.Photo: Pam LeBlanc, staff writer

8of8Visitors to the South Padre Island Birding and Nature Center can climb a five-story tower or stroll a boardwalk.Photo: family photo, special to the American Statesma

I feel like I'm planting a beach-side garden.

The white, ping-pong-ball-shaped orbs I'm placing in a hole in the sand aren't flower bulbs, though. They're sea turtle eggs, laid just a few hours ago.

"You're holding the eggs of one of the rarest reptiles on earth," says Jeff George, executive director of Sea Turtle Inc., a nonprofit organization on South Padre Island that rescues injured sea turtles and works to protect the endangered creatures.

Kemp's Ridley turtles lay their eggs here between April and August, and crews from Sea Turtle Inc. set out on foot and all-terrain vehicles to look for nesting mothers. They spotted one this morning, and when she headed back out to sea, they dug up her 98 eggs and loaded them gently into a Styrofoam ice chest. At Sea Turtle Inc. headquarters, the eggs were counted and recorded.

Now, we're burying them inside a protected corral on the beach, where 30 other egg clusters have been carefully transplanted away from the prying teeth of the island's resident badgers and coyotes. An estimated one in 300 will make it to adulthood.

It's just one highlight of an eco-themed trip to South Padre Island, where you can also explore a birding center, take an ecotour boat ride or learn about the impact of pollution at a marine research lab. And, in between all that, you can play in the waves, build a sand castle, fly high over the water on a parasail, watch the sailboats and windsurfers and dine on local seafood.

For a vacation that's more about nature and the environment than bikinis and beer, hit up these spots.

1 Sea Turtle Inc.

Ila Loetscher, the Turtle Lady of South Padre Island, started taking in sick and injured sea turtles in 1977. She also decked them out in costume, but we'll forgive her because she launched a movement that over the years has saved hundreds of turtles. Loetscher is gone, but the center carries on her mission of rehabilitation, conservation and public education. The star resident is Allison, who lost three flippers in a predator attack as a baby. You can watch her zip around her tank with the help of a prosthetic rudder.

You can also learn about the broader plight the Kemp's Ridley turtles face. In 1947, researchers found about 40,000 nests on a beach in Mexico, their primary nesting ground. Poachers decimated the population, and by 1985, fewer than 500 female sea turtles remained. Thanks in part to an agreement between Mexico and the United States, the nesting grounds were protected and the population rebounded - until recently, when numbers dropped again. Experts are unsure whether the downtick is related to the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 or other factors, like cold snaps that "stun" the animals, making them prone to passing boat props.

The takeaway message? "Be good to the environment, don't trash the beach, look out for turtles and let us know if you see one," says Kat Lillie, assistant curator.

And, if you feel like it, help foot the bill for the center's upcoming $5.2-million expansion, which calls for a face-lift of the existing facility, a new boardwalk over the lagoon, an education center, veterinary clinic, amphitheater, displays and tanks for permanent turtle residents.

Walk more than half a mile along a boardwalk over the wetlands, watching ducks fledge, fish spawn, butterflies flutter by and exotic-looking birds make an appearance. Then climb the five-story observation tower for a birds-eye view of the bay.

Board the Getaway at Sea Ranch Marina and head out to the bay, where the crew drags a net behind the boat. The booty during our trip included a squid, a small butterfly ray, an annoyed-looking blue crab, a trio of starfish, a flounder and a fist-size, slimy-looking sea slug called a Spanish dancer.

Oh, and the dolphins. We saw so many and they came so close a friend accidentally tossed her cellphone overboard. (Don't do that.) In all, about 200 dolphins call this bay home. "We've got a very healthy ecosystem," says deck hand William Zavala. "That's why the dolphins stick around."

At the southern tip of the island, don't miss the humble Coastal Studies Laboratory, part of the University of Texas-Rio Grande Valley. You can peer into a bank of aquariums holding native fish and invertebrates, or inspect a huge whale skull. The lab serves as headquarters for the Marine Mammal Stranding Network. Researchers here whirl into action when critters wash ashore. They also educate the public about keeping beaches clean and healthy.

"We've got a problem with people leaving trash on the beach," says Brigette Goza, senior program coordinator. "We educate the public about how marine life is harmed by that."

When your brain is packed, take to the skies for an overview of the island from a parasail. Several companies offer rides, including Coconuts Water Sports. Passengers strap on harnesses and are slowly reeled up, up and away from the boat. From what seems like outer space, they can peer down on the island and boats far below.